Seismic exploration involves surveying subterranean geological media for hydrocarbon deposits. A survey typically involves deploying seismic sources and seismic sensors at predetermined locations. The sources generate seismic waves, which propagate into the geological medium creating pressure changes and vibrations. Variations in physical properties of the geological medium give rise to changes in certain properties of the seismic waves, such as their direction of propagation and other properties.
Portions of the seismic waves reach the seismic sensors. Some seismic sensors are sensitive to pressure changes (e.g., hydrophones), others to particle motion (e.g., geophones), and industrial surveys may deploy one type of sensor or both. In response to the detected seismic waves, the sensors generate corresponding electrical signals, known as traces, and record them in storage media as seismic data. Seismic data will include a plurality of “shots” (individual instances of the seismic source being activated), each of which are associated with a plurality of traces recorded at the plurality of sensors.
Seismic data is processed to create seismic images that can be interpreted to identify subsurface geologic features including hydrocarbon deposits. However, seismic imaging generally also requires an accurate velocity model to be derived from the seismic data. Conventional methods for building velocity models include moveout analysis such as semblance analysis, tomography, and full waveform inversion. In general, conventional moveout analysis methods are based on 1D picking (analysis at individual x-y surface locations) and can result in lateral inconsistencies in the velocity model. Full waveform inversion can provide velocity models with better lateral consistency but are very computationally expensive.
There exists a need for improved diagnostic characterization of errors in imaging velocity as input to velocity analysis methods that are not computationally expensive that will allow better velocity models to be derived, ultimately leading to seismic images that will allow better seismic interpretation of potential hydrocarbon reservoirs.